Wall display devices, such as electric bulletin boards and advertisement sign boards, are widely used as means for providing information to many and unspecific people on streets. Such a wall display device usually includes a number of display elements arranged on a plane to form a two-dimensional matrix array of pixels in which an individual element is used for a pixel. The respective display elements are electrically actuated in various manner to display information. In an electric bulletin board, for example, one light bulb is used as one display element for one pixel, and a plurality of the light bulbs are arranged in matrix. By illuminating those of the light bulbs in specified positions, it is possible to display letters and pictures. Recently electric bulletin boards using light emitting diodes in place of light bulbs are widely used.
In an advertisement sign board, "panel display elements" are used as display elements to constitute respective pixels. The "panel display elements" are not light emitting themselves but have a plurality of display faces only one of which is actually displayed. Usually one of the display faces to be displayed can be selected by using a rotary mechanism, such as a motor or the like. One display face is selected for each pixel, whereby letters or pictures can be displayed.
Display elements for respective pixels, which are thus provided by light bulbs, light emitting diodes, panel display elements or the like, are electrically actuated. The light bulbs and the light emitting diodes, for example, can be switched between their light emitting state and non-light emitting state by On/Off control of electric power supply. By conducting the On/Off control on the respective light bulbs or the respective light emitting diodes which provide respective pixels, only required pixels can be selectively illuminated, whereby required information can be displayed. In the panel display elements the On/Off control of electric power supply to the motor is conducted, whereby those of the display faces to be actually displayed can be selected. The On/Off control is conducted on the respective panel display elements providing the respective pixels, whereby a required display face for each pixel can be displayed and required information can be displayed.
In the above-described display devices, needless to say, larger numbers of pixels are necessary for improvement of their display resolution. Accordingly it is necessary that a large number of display elements for respective pixels are arranged in a matrix. However, in order to increase a number of display elements, a number of wiring lines for the display elements must be increased. Therefore, a structure of a display device becomes complicated, which need much labor for its manufacture and maintenance. This results in higher manufacturing costs and maintenance costs.
In order to solve such problems, in the International Application No. PCT/JP95/00901 based on the Patent Cooperation Treaty, there is disclosed a novel technology in which a large number of display units having address recognition function are arranged in a matrix form to thereby constitute a display device. In this novel display device, since respective display units have address recognition function, it is possible to respectively independently control individual display units by a common signal through a common transmission passage. Accordingly, even if the number of display elements is increased, there is no possibility that wiring becomes complicated. Namely, if a particular display instruction is to be given to a specific display unit, it is sufficient to give such a display instruction along with address information indicating this specific display unit. When such an approach is employed, even if a common signal transmission passage is used as wiring for the respective display units, the individual display units can judge, by making reference to the address information, whether or not the given display instruction is directed to themselves.
In addition, in the International Application No. PCT/JP96/00058 based on the Patent Cooperation Treaty, there is disclosed a novel display device providing individual display units with memories in which respective display operations are stored in advance. In this display device, since the display units store respective own display operations for themselves in advance, it is possible to execute the display operations stored in advance even if no instruction is given from the external.
An object of this invention is to provide a novel technique for more efficiently operating a display device which provides a large number of display elements in a matrix form corresponding to respective pixels to constitute a two-dimensional pixel arrangement, wherein the respective display elements are driven by electric power to vary their display state.